This invention relates generally to electronic control circuits used as an interface with magneto-optical current sensors that employ the Faraday effect for measuring currents in high voltage transmission lines. More specifically, this invention relates to self-calibrating feedback control circuits that insure constant effective DC components of emerging light intensity free from low frequency variations in light transmission, LED efficiency, or PIN diode radiant sensitivity. With a constant DC component of light intensity, the AC component is directly proportional to the conductor current in the linear range thereby calibrating the sensor.
A common requirement in the application of fiber optical technology is the stabilization of the LED light source to minimize the effects of temperature changes, aging, and radiant sensitivity. In most applications this is accomplished by adding a feedback circuit using the control signal to compensate for drift that may result from these undesirable circuit characteristics.